Adaptive changes of coral Galaxea fascicularis holobiont in response to nearshore stress

Abstract

Global change and local stressors are simultaneously affecting the nearshore corals, and microbiome flexibility may assist corals in thriving under such multiple stressors. Here, we investigated the effects of various environmental variables on Galaxea fascicularis holobiont from nearshore and offshore reefs. These nearshore reefs were more turbid, eutrophic, and warm than offshore reefs. However, coral physiological parameters did not differ significantly. Corals under stressful nearshore environments had low symbiont diversity and selected more tolerant Symbiodiniaceae. The bacterial diversity of offshore corals was significantly higher, and their community composition varied obviously. Diffusion limitations and environmental heterogeneity were essential in structuring microbial communities. Functional annotation analysis demonstrated significant differences between nearshore and offshore corals in bacterial functional groups. Environmental stress significantly reduced the complexity and connectivity of bacterial networks, and the abundances of keystone taxa altered considerably. These results indicated that corals could thrive nearshore through holobiont plasticity to cope with multiple environmental stresses.

Coastal Upwelling Under Anthropogenic Influence Drives the Community Change, Assembly Process, and Co‐Occurrence Pattern of Coral Associated Microorganisms

“…Durusdinium (D1) occurs more frequently in high turbidity and high‐stress regions, so it was not difficult to understand the higher abundance of D1 in the non‐upwelling zone. In addition, nutrients had little effect on the Symbiodiniaceae, which may suggest that the G. fascicularis lacks symbiotic flexibility in dealing with seawater eutrophication in the nearshore reef area where the nutrient concentration changes little (G. Zhou et al., 2017; Zhu et al., 2022c). However, land use was an important factor affecting the Symbiodiniaceae community, indicating that other unmeasured environmental factors that resulted from land use may have played a role.…”

“…In general, we identified different functional characteristics in microbial communities of corals from upwelling and non‐upwelling zones based on FAPROTAX. For example, the abundance of metabolic potential in nearshore corals (non‐upwelling zone) was significantly higher than in offshore reefs (less disturbed), and the changes in functional groups can be attributed to local environmental conditions including nutrients, temperature, and turbidity (Zhu et al., 2022c). In particular, we revealed higher relative abundance of chemoheterotrophy and aerobic chemoheterotrophy metabolisms in corals collected from upwelling than that in non‐upwelling, which are categorized as broad metabolic or ecologically relevant functional groups (Rivett & Bell, 2018).…”

“…The coral probiotic hypothesis suggests that corals rapidly adapt to changing environmental conditions by altering the bacterial community composition (Reshef et al., 2006). The coral core microbiome in the study ( Pseudomonas and Acinetobacter) is essential in the nitrogen cycle and the sulfur cycle of corals; these core microbes enhance the defense ability of the host, resist the proliferation of pathogens, and help degrade pollutants (Reshef et al., 2006; Zhu et al., 2022c). However, while the genus Pseudomonas is known in the core microbiome, it generally only accounts for a small fraction of coral‐associated beneficial bacterial groups (Hernandez et al., 2018; Lima et al., 2022; Röthig et al., 2016).…”

“…The tissue biomass of the coral is the difference between the dry weight (at 50°C for >24 hr) and the ash weight (at 450°C for >4 hr). The Symbiodiniaceae density, protein content, and tissue biomass were standardized to the surface area (Zhu et al., 2022c).…”

“…Some data of the samples from non‐upwelling region, including environmental factors, Symbiodiniaceae sequencing, bacterial amplicon sequencing, Symbiodiniaceae density, and tissue biomass, were published previously in a companion paper (Zhu et al., 2022c). Data on OTUs abundance were randomly resampled to the sequencing depth of the sample with the lowest sequences for Symbiodiniaceae (10049) and bacteria (11070), respectively.…”